Will grinned. "Some of these books are dangerous," he said. "It's wise to be careful.""One must always be careful of books," said Tessa, "and what is inside them, for words have the power to change us.""I'm not sure a book has ever changed me," said Will. "Well, there is one volume that promises to teach one how to turn oneself into an entire flock of sheep-""Only the very weak-minded refuse to be influenced by literature and poetry," said Tessa